Edge gating is well known in the art of injection molding and generally refers to a process for molding a part in which the mold gate is located at an edge or a side of a mold cavity, rather than at the center thereof. In general, the axis along which melt flows into the mold cavities in an edge gating system is at an angle to the main axis of the nozzle. Edge gating is typically used in applications where part geometry dictates that the gate cannot be located at the center of the part or in applications where it is desirable to hide the vestige left by the mold gate on the part. A typical application for edge gating is a molded syringe, which is generally a thin tube, for medical applications.
In a typical edge gated system, a plurality of cavities are located in a cooled cavity plate around a heated nozzle. Thermal gated mold gates are selectively openable to allow melt to flow from the nozzle into the cavities through heating and cooling of the mold gates. Thermal gating requires a heater to be provided along the nozzle and as near to the tip of the nozzle as possible.
There are applications where the mark, or the vestige, left on the edge or lateral gated molded part is not acceptable or should be almost invisible for aesthetic or functional reasons.
Hot runner nozzles for edge gating applications using mechanical means to open and close a mold gate, such as a movable valve pin, rather than thermal means are also known. Valve gated nozzles are presumed to provide a better control of the flow of material through the mold gate. However, there is still a need in the art for edge gating apparatus and methods that provide improved molded parts.